Sport science for salmon and other species: ecological consequences of metabolic power constraints

Abstract

For metabolically demanding behaviours, power supply (ATP resynthesis per unit time) is an important constraint on performance. Yet ecology as a discipline lacks a framework to account for these power constraints. We developed such a framework (borrowing concepts from sports science) and applied it to the upriver migration of anadromous fish. Our models demonstrate how metabolic power constraints alters optimal migratory behaviour; in response to strong counter flows, fish minimise cost of transport by alternating between rapid, anaerobically fuelled swimming and holding to restore spent fuels. Models ignoring power constraints underestimated the effect of elevated water temperature on migration speed and costs (by up to 60%). These differences were primarily due to a temperature-mediated reduction in aerobic scope that impairs the ability of fish to rapidly migrate through warm waters. Our framework provides a mechanistic link between temperature-induced reductions in aerobic scope and their ecological consequences for individuals, populations and communities.

Living in flowing water increases resistance to ultraviolet B radiation

“…In a natural context, exercise is necessary for fitness-related activities such as behavioural interactions, dispersal and predator-prey interactions (Irschick and Garland, 2001;Martin et al, 2015;Sinclair et al, 2014). UV-Bmediated oxidative damage to muscles and the resulting decreases in locomotor performance therefore can have far-reaching ecological consequences.…”

Climate change impacts on animal migration

“…A new theoretical model now suggests that in Chinook salmon, metabolic constraints exacerbate the effect of temperature on the metabolic costs of migration [6]. Salmon often migrate hundreds of kilometres from their natal riverine areas to the ocean and return to their natal areas for spawning.…”

“…But even at more benign temperatures that nonetheless diverge from the optimal range, decreases in physiological performance increase ecological failure by impairing movement [5]. Hence, changing environmental temperatures, including changes resulting from anthropogenic global warming, impact migration and other ecological processes via the thermal sensitivity of physiological processes.A new theoretical model now suggests that in Chinook salmon, metabolic constraints exacerbate the effect of temperature on the metabolic costs of migration [6]. Salmon often migrate hundreds of kilometres from their natal riverine areas to the ocean and return to their natal areas for spawning.…”

“…If fish did not have to replenish metabolic substrates (in particular glycogen) during their migration, the effects of warm water could be mitigated by swimming through warm sections of river rapidly. However, the need to replenish substrates by resting in tranquil warm water increases migration times and therefore exposure to warm waters [6]. Replenishment of substrates and increased exposure to warm water reduce the metabolic scope, that is the energy available for migration, because metabolic maintenance costs increase in warmer water.…”

“…These effects are amplified because cardiovascular efficiency is compromised as temperatures increase beyond optimal ranges, thereby further reducing metabolic scope. These physiological dynamics mean that climate warming along the North American west coast has already affected salmon migration [5,6]. The examples from salmon emphasise that predictions of future effects of climate change require detailed physiological studies.…”